Chill out. Its not that crucial.
I'm sorry to say that I seriously doubt that US will survive this, especially if DCA is closed for an extended amount of time. That's a good source of business traffic and they really can't afford to lose it. UAL also might not survive, as they really can't seem to get away from red ink, and this will not help them see black. I tend to agree with the Delta boys (Delta_fan, DeltaOwnsAll) DL will probably be the largest airline in the world after this all clears up. They are in decent shape. NW also may not make it. They don't really usually lose a lot of money, but then again they don't normally make a lot either. If they survive it will be due to their excellent service and such.
CO, WN, and B6 will come out of this fine. AA, I'm not too sure what's going to happen there, but I predict that they will survive. US will only survive if UA goes under, or significantly downsizes. They will be the first to attempt to develop a new hub out west in one of UA's old stomping grounds (DEN or LAX). CO will also do the same. But really I only see these airlines surviving a few years from now.
Maybe, maybe not:
Just my opinion. Don't flame me talking about "Northwest is not going under!!!!, Don't doubt United!" etc.
God bless those affected by Tuesday's events.